EP06.14: Early hub organization and progressive strengthening of the structural connectome in the normal fetal brain

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Objectives: Previous studies have shown that structural connectivity increases during gestation; however, little is known about whether this reflects progressive network reorganization or strengthening of an already established architecture.We aimed to distinguish between these two developmental patterns.Methods: In this prospective study, healthy fetuses between 21 and 36 weeks of gestation underwent in-utero DTI on a 1.5-T MRI system.Whole-brain structural connectomes were reconstructed from 30 atlas-defined regions of interest (ROIs).Global connectivity, regional nodal strength (sum of streamline counts connecting a region to all other regions) and pairwise connections were quantified using streamline counts.Associations with gestational age (GA) were assessed using linear regression models.Hub regions were defined as the top 20% of regions with the highest nodal strength.Stability of regional connectivity across gestation was evaluated using Kendall rank correlation across three GA subgroup (<28, 28-31.9,≥32 weeks).Results: Forty-seven fetuses were included: 15 <28 weeks, 16 between 28 and 32 weeks, and 16 > 32 weeks.Global structural connectivity increased significantly with GA (β = 0.086 per week, R 2 = 0.42, p < 0.001).At the regional level, 25 of 30 ROIs demonstrated significant connectivity strengthening with GA (q < 0.05), with the strongest effects observed in cerebellar, frontal and cingulate regions (R 2 up to 0.51).Bilateral frontal and occipital lobes, and vermian region were consistently identified as the principal hubs across gestation with high concordance of regional ranking (Kendall t = 0.83-0.90). Conclusions:The fetal structural connectome strengthens progressively during gestation while preserving its regional hierarchy.The presence of stable hubs from the earliest gestational subgroup suggests that hub organization is already established by midgestation and subsequently reinforced.